The conversion of alcohols to hydrocarbons is generally not commercially feasible. In fact, the majority of commercial alcohols are produced from hydrocarbons. Alcohol-to-hydrocarbon conversion is further prohibitive due to the significant cost requirements of current conversion processes. In particular, alcohol from natural means (e.g., by fermentation of biomass) would be a significantly more cost-efficient feedstock for a conversion process.
However, a major obstacle in applying current conversion methodology to biomass-produced alcohols (i.e., bio-alcohols) is the high concentration of water (and concomitant low alcohol concentrations) typically encountered in fermentation streams produced in biomass-to-alcohol refineries. Current alcohol-to-hydrocarbon conversion processes are generally incapable or highly ineffective in providing such conversion at such dilute alcohol and high water concentrations. Instead, current alcohol-to-hydrocarbon conversion processes generally require pure alcohol (i.e., in the substantial absence of water). Yet, concentration and/or distillation of alcohol from a fermentation stream to accommodate current technologies would be highly energy intensive, and thus, would largely offset gains made in the initial low cost of using a bio-alcohol.
Another significant obstacle in existing alcohol conversion processes is the unacceptably high level of benzene produced in the hydrocarbon fraction, generally up to about 5% benzene content. However, governing environmental regulations generally require a much lower benzene content for use as a fuel. For example, in the U.S., the Environmental Protection Agency (EPA) has recently imposed a benzene limit of 0.62 vol %. Thus, a further advantage would be provided by an alcohol conversion process that could produce a hydrocarbon blendstock with a substantially reduced benzene content.